FIG. 14 shows a conventional organic EL element disclosed in the Patent Document 1 described below. The organic EL element X is formed on a transparent substrate 91 and includes a reflection film 92, an anode 93, an organic layer 94 and a cathode 95. The reflection film 92 is made of metal. The anode 93 is a multilayer transparent electrode. The organic layer 94 comprises a hole injection layer 94a, a hole transporting layer 94b, a light emitting layer 94c, an electron transporting layer 94d and an electron injection layer 94e. The cathode 95 is a transparent electrode.
When a voltage is applied between the anode 93 and the cathode 93, the light emitting layer 94c positioned between these emits light. The light directed upward in the figure passes through the cathode 95 to exit to the upper side of the organic EL element X. On the other hand, the light directed downward in the figure passes through the anode 93 and is reflected by the reflection film 92. The light then passes through the anode 93, the organic layer 94 and the cathode 93 to finally exit to the upper side of the organic EL element X. In this way, the organic EL element X emits light to the side opposite from the transparent substrate 91 located on the lower side. This structure is called a top emission type.
Generally, the cathode 93 is formed by performing sputtering, molecular beam epitaxy (hereinafter referred to as “MBE”) or ion plating with respect to the material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) In these techniques, however, the organic layer 94 is heated to a high temperature exceeding 100° C. Thus, the organic layer 94 may be damaged chemically. Further, in the above-described techniques, the particles such as atoms, molecules or ions constituting ITO or IZO are caused to hit against the organic layer 94. Thus, the organic layer 94 inevitably receives physical damages. These damages may lead to abnormality of the characteristics of the organic EL element such as an increase in power consumption or a decrease in luminance.
Patent Document 1: JP-A-2004-247106